1. Field of the Invention
The present invention relates to a composition comprising at least one organofluorine-functional silane and/or siloxane, to a process for preparing it and to its use and also to correspondingly surface-modified substrates.
2. Discussion of the Background
It is known to prepare a composition comprising at least one organofluorine-functional silane and/or siloxane by mixing, by controlled acid- or base-regulated hydrolysis, or by condensation or cocondensation of organofluorine-functional chlorosilanes and/or alkoxysilanes, with or without further precursor components. Besides organic or inorganic acids or bases, pH regulation in this case is carried out using acidic or basic salts, such as alkali metal carbonate, alkali metal hydrogen sulfate, alkali metal dihydrogen phosphate, magnesium hydroxide or aluminum acetate. In the preparation of the compositions it is also known, for example, to employ other hydrolyzable organosilanes, silicon, titanium or zirconium tetrachlorides, or corresponding metal-acid esters as precursor components.
Compositions of this kind, containing water, solvent or dispersant, are generally employed for giving substrates a hydrophobic and at the same oleophobic and dirt-repellent finish, or else, for example, a hydrophilic finish, or for the special modification of the surface properties of the substrates, for example, for metals, metal oxides, fillers, pigments, glass, enamel, ceramic, construction materials, buildings, fibers, textiles, natural substances, plastics, and coating materials. This modification may involve the formation of a protective layer against UV radiation or mechanical, thermal and chemical influences. Furthermore, scratch proofing, anticorrosive, antiicing, antifouling, antibacterial or antithrombic properties may also be obtained. Besides the organic functional groups, said silane and/or siloxane systems generally possess Si-bonded hydroxyl and/or alkoxy groups, which are intended to permit subsequent attachment to the substrate. However, it is often difficult to achieve satisfactory and permanent attachment of the coating to the substrate.
DE 196 46 662 A1 describes the treatment of a metal surface with an SnCl2 solution followed by application of amino-functional alkoxysilanes, giving coatings resistant to moisture and corrosion.
Stable hydrophobic coatings on steel can be prepared by combining alkoxides, methyl alkoxides, such as Al(CH3)(OC2H5)2, or acetonates of the metals Al. Zr, Ti, Si, W, Ce, Y or Sn with fluoroalkylalkoxysilanes, as is disclosed, for example, in JP 1068477. Similarly, in accordance with JP 4136181, nonmetals can also be given permanent hydrophobicization.
Finally, EP 0 799 873 A1 discloses the preparation of water- and oil-repellent coatings by application of a composition comprising an aqueous solvent, such as alcohol, a fluorinated alkoxysilane, and a Brxc3x6nsted acid and/or Brxc3x6nsted base catalyst.
It is an object of the present invention to provide a composition having improved adhesion properties and crosslinking properties on a polar substrate surface and, therefore, better coating properties.
This object is achieved in accordance with the invention as specified in the claims.
It has surprisingly been found that a highly reactive composition comprising organofluorine-functional silanes and/or siloxanes which carry some silanol groups in addition to hydrolyzable groups is obtained by mixing at least one organofluorine-functional chlorosilane or alkoxysilane and, optionally, further organofunctional, hydrolyzable silanes, such as organochloro- or organoalkoxysilanes, in the presence of a small amount of water and in the presence of at least one metal salt of aluminum(III), tin(II), tin(IV), iron(III) or titanium(III) and at least one mineral acid, suitably in an organic solvent or dispersant, such as in an alcohol, and subjecting this mixture, optionally, to partial hydrolysis and, optionally, to condensation or oligomerization.
By applying the present composition to a substrate it is possible, surprisingly and advantageously, to obtain a particularly well-adhering and permanent coating. In general, the reactive Si compounds in the composition are in the form of reactive monomeric units. Compositions of the invention can, however, also be formulated so that oligomeric Si compounds predominate.
Furthermore, despite their high reactivity, compositions of the invention are, surprisingly, stable for relatively long periods, generally more than 5 months. In addition, the composition of the invention is immediately ready to use and is comparatively simple to apply, for example, by dipping, spraying or polishing, since the composition obtained in accordance with the invention is notable for a particularly rapid and complete reaction with a polar surface. In general, application of the composition of the invention immediately produces a homogeneous, highly crosslinked coating which, depending on the functionality of the organic groups, is outstandingly suited to the full and permanent, chemically bonded, organic modification of polar substrate surfaces. In this context, said metal salts act in conjunction with said mineral acids as catalyst.
The present invention therefore provides a composition comprising at least one organofluorine-functional silane and/or siloxane, at least one mineral acid, and at least one metal salt of aluminum(III), tin(II), tin(IV), iron(III) or titanium(III).
The metal salt content of the composition of the invention is preferably from 0.01 to 10% by weight, especially from 0.01 to 1% by weight, based on the composition.
The composition of the invention also includes as mineral acid preferably hydrogen chloride, nitric acid, phosphoric acid or sulfuric acid, the mineral acid content preferably being from 0.001 to 5% by weight, especially from 0.01 to 1% by weight and, with very particular preference, from 0.05 to 0.5% by weight, based on the composition.
The composition of the invention suitably includes a solvent and/or dispersant. For example, it may include an aromatic hydrocarbon or an aliphatic hydrocarbon or an alcohol or water, or a mixture thereof. Methanol, ethanol, n-propanol, isopropanol, n-butanol, acetone, cyclohexane, n-hexane or toluene, in particular, can be employed advantageously as solvent. In general, the amount of solvent and/or dispersant makes up the sum of the components of the composition of the inventionxe2x80x94organosilanes and/or organosiloxanes, mineral acid, metal salt and, optionally, waterxe2x80x94to 100%.
Compositions of the invention preferably comprise those silanes and/or siloxanes which comprise organofluorine-functional groups, especially fluoroalkyl-functional groups of the formula CF3(CF2)m(CH2)nxe2x80x94 where m=0 to 18 and n=0 or 2, examples being tridecylfluorooctyl {(C6F13)xe2x80x94(CH2)2xe2x80x94}, heptadecafluoro-decyl {(C8F17)xe2x80x94(CH2)2xe2x80x94}, nonafluorohexyl {(C4F9)xe2x80x94(CH2)2xe2x80x94}, heneicosafluorodecyl {(C10F21)xe2x80x94(CH2)2xe2x80x94}, 3,3,3-trifluoropropyl {(CF3)xe2x80x94(CH2)2xe2x80x94} or 3-(1,1,2,2-tetrafluoro-ethoxy)propyl {(HC2F4)xe2x80x94Oxe2x80x94(CH2)3xe2x80x94} groups, optionally, aminoalkyl groups, examples being 3-aminopropyl, N-2-aminoethyl-3-aminopropyl or N-2-aminoethyl-Nxe2x80x2-2-aminoethyl-3-aminopropyl, and also vinyl groups, methacryloxyalkyl groups, an example being 3-methacryloxypropyl, and also alkyl groups, examples being methyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-octyl, isooctyl and hexadecyl, or cycloalkyl groups, examples being cyclopentyl and cyclohexyl, or cycloalkylene groups, examples being cyclohexenyl, cyclooctenyl and cyclododecadienyl groups, and also epoxyalkyl and epoxycycloalkyl groups, such as 3-glycidyloxypropyl or 2,3-epoxycyclohexyl groups, the siloxane containing not more than one of said organofunctional groups attached to one silicon, whose other valences are occupied by xe2x80x94Oxe2x80x94Si bonds or OH groups and, optionally, by alkoxy groups or chloro substituents.
The present invention additionally provides a process for preparing a composition of the invention by mixing, optionally partially hydrolyzing, and, optionally, condensing at least one organofluorine-functional silane and, optionally, further organofunctional silanes in the presence of water, at least one mineral acid and at least one metal salt of aluminum(III), tin(II), tin(IV), iron(III) or titanium(III).
The amount of water present in the process of the invention is, suitably, low. The amount of water in this case is preferably from 1 ppm by weight to 2% by weight, more preferably from 10 ppm by weight to 1.5% by weight, with very particular preference from 0.01 to 1% by weight and, with special preference, from 0.05 to 0.3% by weight, the figures for the amount of water being based on the amount of silanes employed and including water of crystallization.
In the process of the invention, the silanes to be mixed or hydrolyzed, and, optionally, condensed are suitably introduced initially, as a mixture, and the metal salt, mineral acid and, optionally, water components are added simultaneously or successively to this initial charge.
Mixing, hydrolysis or condensation of the silanes employed is suitably conducted in a solvent or dispersant. In particular, an aromatic hydrocarbon, such as toluene, or an aliphatic hydrocarbon, such as cyclohexane, or an alcohol, such as methanol or ethanol or isopropanol, or a mixture thereof can be used for this purpose. This generally produces clear, stable solutions or metastable dispersions, which are normally stable for longer than 5 months on storage.
In the process of the invention it is preferred to employ the following silanes:
organofluorine-functional silanes of the general formula (I)
F3C(CF2)m(CH2)nSiR1yX(3xe2x88x92y)xe2x80x83xe2x80x83(I)
in which X is chloro or a group RO and R is a linear or branched alkyl radical of 1 to 4 carbon atoms, R1 is a linear, branched or cyclic alkyl group of 1 to 8 carbon atoms, n=0 or 2, y=0 or 1 or 2 and m=0 to 18, such as 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl -trimethoxysilane, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl-trichlorosilane, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane, 3,3,4,4,xe2x88x925,5,6, 6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl-triethoxysilane, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,xe2x88x9210,10,10-heptadecafluorodecyl-trichlorosilane, 3,3,xe2x88x924,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-decyltrimethoxysilane, 3,3,4,4,5,5,6,6,6-nonafluoro-hexyltriethoxysilane, 3,3,4,4,5,5,6,6,6-nonafluoro-hexyltrimethoxysilane, 3,3,4,4,5,5,6,6,6-nonafluoro-hexyltrichlorosilane, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10,11,11,12,12,12-heneicosafluorododecyltri-ethoxysilane, 3,3,3-tri-fluoropropyltrichlorosilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane or 3-(1,1,2,2-tetra-fluoroethoxy)propyltrimethoxysilane or 3-(1,1,2,2-tetrafluoroethoxy)propyltrichlorosilane and, optionally,
further silanes, examples being:
amino-functional organosilanes, such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-Nxe2x80x2-2-aminoethyl-3-aminopropyltrimethoxysilane, bis(3-triethoxysilylpropyl)amine, and bis(3-trimethoxysilylpropyl)amine,
epoxy-functional organosilanes, such as 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, and 2-(2,3-epoxycyclohexyl)ethyltrimethoxysilane,
alkylsilanes, such as methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, octyltrichlorosilane, octyltriethoxysilane, isooctyltrimethoxysilane, hexedecyltrimethoxysilane, and octadecyltrichlorosilane,
cycloalkylsilanes, such as cyclohexyltrimethoxysilane, cyclopentyltri-chlorosilane, and cyclohexyltriethoxysilane,
cycloalkenylsilanes, such as cyclohexenylethyl-triethoxysilane, cyclododecadienyltrichlorosilane, cyclooctenyltrimethoxysilane,
and also tetraethoxysilane and also vinyltrimethoxysilane, vinyl triethoxysilane, vinyltris(methoxyethoxy)silane or 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane.
Furthermore, the respective silanes can be employed with one another in various proportions and also with the same functionalities or with two or more different functionalities. Preferably, the amount of organofluorine-functional silanes and/or organofluorine-functional siloxanes in the composition of the invention is adjusted to from 0.01 to 10% by weight, more preferably from 0.1 to 5% by weight and, with very particular preference, from 0.25 to 3% by weight, based on the composition.
In the process of the invention, moreover, the metal salt is preferably employed in solid or liquid or dissolved form. The metal salt employed is suitably a chloride, nitrate, sulfate, hydrogen sulfate, phosphate, hydrogen phosphate or dihydrogen phosphate. Particularly preferred metal salts are metal chlorides -especially aluminum(III) chloride, tin(II) chloride, tin(IV) chloride, titanium(III) chloride and iron(III) chloride. The metal salt is suitably employed in an amount of from 0.01 to 10% by weight, based on the finished composition.
The mineral acid employed in the process of the invention is preferably hydrogen chloride, nitric acid, phosphoric acid or sulfuric acid in an amount, based on the molar mass of the mineral acid and on the subsequent composition, of suitably from 0.001 to 5% by weight. The mineral acid can be employed in concentrated or aqueous form.
In general, the process of the invention is conducted as follows:
Generally, the silane is introduced initially. It is also possible to add the solvent and/or dispersant. Subsequently, the metal salt, mineral acid and, optionally, water components are added, suitably with thorough mixing. Alternatively, the components can be added either simultaneously or successively to an undiluted or partially hydrolyzed silane or mixture of silanes. Mixing, reaction and aging take place in general under an inert gas blanket at a temperature from 10 to 40xc2x0 C. for from xc2xd to 72 hours, preferably at room temperature (from 15 to 25xc2x0 C.) for a period of from 1 to 24 hours, with particular preference for from 5 to 12 hours. The aging of the mixture can suitably take place with stirring. Alternatively, the preparation can be conducted at a temperature of up to 50xc2x0 C. with or without the use of a stirrer and a condenser, over a period of from xc2xc to 24 hours. The resulting composition can be diluted by adding a solvent or dispersant.
The metal salt employed normally remains in the composition of the invention and so, when the composition of the invention is used, the catalyst present supports in particular the attachment and condensation of the silane and/or siloxane to the substrate surface, in a surprisingly good and thus advantageous manner.
The composition of the invention obtained as described above can be applied to substrates or workplaces by dipping, polishing, spraying or brushing, the thickness of the coating having no particular limitation but being preferably between 0.1 nm and 1000 xcexcm, more preferably between 0.5 and 50 nm and, with very particular preference, between 1 and 15 nm. The treatment time is generally from a few seconds up to about 1 hour, preferably from about 1 to 20 minutes, the duration being critical in some cases for the homogeneity of the coating but generally not for its thickness. Treatment may be followed by a drying time of from 10 seconds to 3 hours at temperatures from 20 to 200xc2x0 C. Drying normally takes place at from 80 to 150xc2x0 C. over a period of from 5 to 20 minutes. The drying operation can be conducted in air, in vacuo, or under an inert gas, such as argon or nitrogen. Examples of preferred substrates that may be used are wood, natural fibers, metals, metal oxides, glass, ceramic, enamel, plastics, stone, synthetic stone, marble, concrete or bitumen.
The present invention therefore also provides for the use of a composition of the invention for coating surfaces, preferably polar surfaces. Examples of such polar substrates are glasses, such as quartz glass or borosilicate glass, metals, such as steel, copper, silver, aluminum, or alloys, such as brass, porcelain, clinker, enamel, minerals, and natural substances, such as silk, sisal or hemp.
Surfaces of plastic with polar functionalities, such as in the case, for example, of polyamide, polycarbonate, phenolic, furan and epoxy resins, polystyrene or polyesters, can likewise be permanently modified. The high degree of crosslinking achievable, furthermore, enables substantially apolar substrate surfaces, such as in the case, for example, of polypropylene, polyethylene or polymethyl methacrylate, to be given a stable coating.
The present invention provides, furthermore, surface-modified substrates obtainable by coating with the composition of the invention. Such surface modified substrates preferably have a coating with a thickness of from 0.1 nm to 1000 xcexcm, more preferably from 0.1 to 500 nm.
Surface-modified substrates obtained in accordance with the invention are also notable outstandingly for excellent water, moisture, heat, acid and alkali resistance and for their UV stability. The adhesion of the coating to the substrate is generally outstanding provided that the development of chemical bonds to the surface is possible in principle, and is also long lasting and likewise combines excellent mechanical strength with flexibility and elasticity.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.